An integrated circuit (IC) typically includes a large number of electronic components, such as resistors, transistors, capacitors, etc., on a chip of semiconductor material. The semiconductor IC industry has experienced rapid growth in the past several decades. Technological advances in semiconductor materials and design have produced increasingly smaller and more complex circuits. As the geometry size of an IC decreases, the practical significance of an electromigration (EM) effect of the IC increases. EM is the transport of material caused by gradual movement of ions in a conductor/resistor. A resistor under operation in an IC generates heat and increases temperature of the IC, which is known as Joule heating. EM is exacerbated by a high Joule heating of the resistor, which can lead to eventual failure of electrical components in the IC.
The thermal distribution of a resistor under operation is typically not uniform. According to the physical structure of the resistor, contacts at two sides of the resistor are connected to colder devices or metals, to serve as heat dissipation paths. While lower temperatures can be observed at the two sides of the resistor, the resistor's center area forms a thermal hot spot. In this case, the resistor's center area has the highest temperature and forms the weakest point in terms of EM. Especially, the center temperature of the resistor becomes higher when the resistor has a larger length and/or a larger current. While conventional techniques use edge contacts to relax temperatures at a resistor's edges by heat dissipation, the resistor's center remains as a hot spot and an EM critical area. Thus, conventional techniques for heat dissipation of resistors in an IC are not entirely satisfactory.